1. Field
Example embodiments relate to an image sensor and a fabrication method thereof. Other example embodiments relate to an image sensor capable of reducing dark current and a fabrication method thereof.
2. Description of the Related Art
An image sensor is a semiconductor device that converts an optical image into an electrical signal. Image sensors may be classified into charge coupled devices (CCD) and complementary metal-oxide semiconductor (CMOS) image sensors. A CCD refers to a device in which the MOS capacitors are more closely arrayed and charge may be stored in a capacitor. A CMOS image sensor refers to a device which uses a switching method. A CMOS image sensor may have the same amount of MOS transistors as pixels and a control circuit. The CMOS image sensor also may have a signal processing circuit that is used as a peripheral circuit and the output may be sequentially detected by the MOS transistor. The CMOS image sensor may include a photodiode that receives light into a unit pixel and CMOS may block controlling image signals from the photodiode.
A trench-type field insulation layer may be formed in a CMOS image sensor in order to isolate actives and fields. An interface between a field insulation layer and an active region may be damaged during the formation of the field irysulation layer. The damage to the interface may generate a hole carrier, thereby increasing a leakage current of a photodiode. This leakage current may move into the floating diffusion region from the photodiode and this current is called dark current.